A flute is a type of wind instrument in which the impingement of air on an edge as the air passes into a sound chamber causes the air to oscillate to produce an audible tone. One type of flute is a whistle flute or fipple flute, which employs a whistle-type mouthpiece and is among the most ancient of all musical instruments. In this family are the recorder (also known as the fipple flute or English flute), the flageolet, and the ocarina (also known as the globular flute or the vessel flute). The ocarina dates back to antiquity and is reported to be of South American or Central American descent, though there are indications of its use in other parts of the ancient world.
Most types of wind instruments employ an open-ended tubular- or conical-shaped cavity to produce sound, whereas ocarinas utilize an enclosed sound chamber or cavity. Ocarinas have at least one airway that directs an airstream across a fipple window to impinge upon a fipple edge, at least one sound chamber, and a plurality of toneholes that penetrate into the enclosed chamber and that are used to control the pitch sounded by the instrument.
Ocarinas may be fabricated from a variety of materials, such as ceramics, wood, metal, plastics, and the like. Many ocarinas sold commercially are not manufactured to the strict dimensional tolerances necessary to consistently produce acoustically excellent instruments. Nevertheless, major challenges are faced by manufacturers who do attempt to craft concert-worthy ocarinas from wood, metal, or other quality machinable materials. The tremendously precise and detailed handwork needed to produce musically superior ocarinas out of these materials requires skilled artisans and is very time consuming. Such a process is costly to both the manufacturer and consumer.
Other challenges encountered in the manufacture of quality ocarinas are related to excessive moisture. First, ocarinas made entirely of wood, while attractive in appearance, are subject to mold, mildew, swelling, shrinking, cracking, and to fluctuations in the vital tolerances of the airway. The above problems result primarily from moisture in the ocarina player's breath, which is blown through the airway and into the sound chamber. Second, ocarinas made entirely out of certain dense, hard machinable materials such as stainless steel, aluminum, or brass suffer from a different problem related to excessive moisture. Because of the high thermal conductivity of these materials, excessive condensation is quick to form in the ocarina airway as the ocarina player blows humid air through it. This build up of condensation causes the fading of notes, especially the notes at the higher end of the octave.
In the case of quality ocarinas molded entirely of some type of plastic resin, there are esthetic design challenges that stem from practical limitations as to how thickly a particular resin can be molded without the occurrence of sagging and shrinking.